The invention is in the technical area of the production of flat electrical structures with a substrate and an electrically conductive coating applied thereon and relates to the electrical contact composite of flat electrical structures as well as methods for producing electrical contact composites.
Flat electrical structures with a substrate of an electrically insulating material and an electrically conductive coating applied thereon are sufficiently known per se. They are frequently used as transparent or opaque panel heating elements, in particular in the form of heatable glazings. Examples of this include heatable windshields, rear windows, glass roofs, or side windows in motor vehicles or wall-mounted or freestanding heating elements in living spaces, which serve to heat the living spaces. However, they can likewise also be used as heatable mirrors or transparent decorative elements. An alternative use of the conductive coating is as a planar antenna for receiving electromagnetic radiation. Flat electrical structures have already been described many times in the patent literature. Merely by way of example, reference is made in this regard to the patent applications DE 102008018147 A1, DE 102008029986 A1, DE 10259110 B3, and DE 102004018109 B3.
As a rule, the electrically conductive coating is electrically connected to at least one electrode. Thus, generally, a single electrode serves in planar antennas for the coupling of electrical signals out of the conductive coating. In panel heating elements, the conductive coating is typically electrically connected to at least one pair of strip- or band-shaped electrodes (bus bars), which are intended to introduce the heating current as uniformly as possible into the conductive coating and to distribute it broadly.
It is customary, in a flat electrical structure, to electrically connect the at least one electrode to a metal contact element to form an electrical contact composite, for example, to connect the conductive coating to downstream antenna electronics (e.g., amplifier circuit) or to the two terminals of a current/voltage source making the heating current available.
It has been demonstrated in practice that such a contact composite is subject to high wear and can break, which may even be accompanied by substrate breakage (e.g., glass breakage). Since this results in a complete functional failure of the panel heating element, which always requires repair by service personnel, it is desirable to implement the contact composite in as stable a manner as possible. However, this undesirably increases production costs.